Leak valve



J. T. GREEN Dec. 7, 1965 LEAK VALVE Filed March 1, 1963 INVENTOR.

Joe T. Green ATTORNEY.

United States Patent 3,222,026 LEAK VALVE Joe T. Green, Orlando, Fla, assignor to the United States of America as represented by the United States Atomic Energy Commission Filed Mar. 1, 1963, Ser. No. 262,278 3 Claims. (Cl. 2515) This invention relates generally to fluid flow regulating devices, and more particularly to a pressure regulated leak valve for the control of gas flow.

In the operation of electromagnetically operated equipment for the separation of isotopes of elements, generally referred to as the calutron, and disclosed in such representative patents as Brackney 2,847,635; Carter 2,806,143; Lyshon 2,802,108; and Barnes 2,794,923, it is desirable to start the arc prior to introduction of the feed material. The initiation of the arc is accomplished by the ionization of a gas fed into the arc chamber from an external source. This manner of operation permits the ionization chamber to be heated to operating temperature as well as allowing the system to be checked for proper operation before admitting the feed material. It is important to condition the system for operation before risking loss of feed materials, as they are often expensive, and scarce and need to be accounted for.

The gas used to start the arc in the source, and which is also employed as support gas during the operation, is usually nitrogen, since it readily ionizes and is relatively inert. However, the regulation of nitrogen flow is sensitive since the range of permissible change in flow varies from about 1 to 20 cc./min., and is usually less than cc./min. The support gas must be kept flowing at a relatively constant rate because slight variations will cause a change in the intensity of the arc, thus resulting in poor focus at the receiver, as the ion beam produced by the arc travels in an arcuate path to the receiver or collector located at the focal point 180 away. Most commercial .valves, however, are not suitable for such a fine adjustment as is required in this system.

The prior art method for regulating the nitrogen flow is to use a machined needle valve. These valves must be .machined to a very close tolerance and as a result are expensive (approximately $35.00 each). An inherent difliculty in valves of this type which have a close fitting tapered needle and corresponding seat is that of galling at the point of contact. Once galled, the needle and seat are permanently damaged and the entire valve must be replaced. The normal replacement rate of such valves has been about two per week. Another fault of the prior art valve is that two people are required to make adjustments. The operator notices a need for valve flow adjustment at the control panel, located remote to the calutron, but the leak valve is located adjacent to the calutron sources, thus requiring someone to assist the operator while communicating by telephone. Obviously this sort of arrangement does not lend itself to very fine adjustment, and, as a result, the operators are usually satisfied with an approximate adjustment or to take a best as we can do attitude toward adjustment.

The flow of very small quantities of gas to a spectrometer for analysis or for experimental purposes has been controlled by a capillary leak which employs a metal tube having an intermediate portion wrapped around and secured to a rotatable shaft. See Nier, 2,422,921. However, such an arrangement would not be suitable for use in calutrons and other systems where large volumes of different gases are handled on a production basis. Some of these gases are of a corrosive nature and it would be difficult to find a metal tube suitable for contact therewith. Nor is such a valve well adapted for remote con- "ice trol, but would require two operators, one to observe the control panel and the other to make the adjustment. The frequent bending or distortion of the metal tube, such as would occur in routine production control, would result in early rupture capillary tubes due to fatigue, and the construction employed by patentee does not permit easy and rapid repair when maintenance is necessary.

Applicant with a knowledge of the problems of the prior art has for an object of his invention the provision of a pneumatically controlled leak valve for regulating gas fiow which can easily and accurately control the flow of gas therethrough.

Applicant has as another object of his invention the provision of a pneumatically controlled leak valve for regulating gas flow which is adapted to be operated by remote control.

Applicant has as another object of his invention the provision of a pneumatically controlled valve for regulating gas flow that can be easily and cheaply maintained.

Applicant has as a further object of his invention the provision of a pneumatically controlled leak valve that is subject to minimal attack by normal corrosive gases.

Applicant has as a still further object of his invention the provision of a pneumatically controlled leak valve that can be easily fabricated and at low cost.

Other objects and advantages of my invention will appear from the following specification and accompanying drawings, and the novel features thereof will be particularly pointed out in the annexed claims.

In the drawings, FIG. 1 is a perspective, partly in section, of my improved leak valve, FIG. 2 is an elevation of the spindle of my improved leak valve.

Referring to the drawings in detail, 1 designates a hollow expandable core of any suitable flexible material that may be easily expanded without rupture, such as natural rubber, plastic or the like. The expandable core 1 is preferably constructed so that it has thick walls and a small bore 13 into one end of which is pressed or threaded a suitable plug 6 made of brass or other acceptable material for closing it. The opposite end of the expandable core 1 receives the reduced end of air supply fitting 9, such as Hansen quick-coupler, to define the spindle. Fitting 9 is preferably of metal and is permanently secured to a plate 14. This plate, which is preferably mounted on the body 7, 7 of the leak valve by a screw or other suitable means (not shown), also serves, when mounted, to maintain the parts of the spindle in assembled relation. The outer free end 10 of the fitting 9 is reduced and carries an annular rib 15 adapted to engage the inner wall of a removable flexible hose, or a mating portion of a conventional commercially available coupling, as it is slipped over the end 10 to retain the hose in place.

Disposed about the expandable core 1 is a two part tubular liner 2, 2 comprised of opposed semi-cylindrical portions. The liner is preferably made from a sheet of Teflon and is adapted to enclose the expandable core 1 and providea lubricated surface between it and a gas vapor tube 4. The vapor tube 4 may be made of any suitable material such as neoprene, butyl, hycar, or hypalon, and is wrapped spirally around the outer surface of the liner 2, 2. A second liner 5 of tubular configuration is wrapped around the vapor tube 4 and this assembly lies between the expandable core 1 and the walls of the bore or cylindrical cavity 3 in the body 7. This second liner 5 is interposed between the spirally wound tube 4 and the walls of bore 3 and is preferably made of Teflon to provide lubrication for the surface engaged by either of its faces.

The above assembly is housed in a two part body 7, 7 of micarta or other suitable material, and is maintained in assembled relation by bolts 16 that pass therethrough. When assembled, the body 7, 7 defines a cavity or bore 3, mentioned above, that receives the control assembly with gas vapor tube 4 wrapped spirally around the expandable core land liner 2, 2 so that as the ex pandable core 1 is expanded under the influence of pneumatic pressure, the turns of the spirally wound tube 4 are pressed against the liner 5 and the inner Walls of the bore of the cavity 3 and are thus constricted and distorted in such a manner as to restrict flow through the tube 4. As shown, the opposite ends of the gas vapor tube pass out through openings in the upper half of body 7, 7, and the forward end of the body is closed by a closure plate 8 which is attached thereto by screws 17 or other appropriate means. This closure plate adds rigidity to the body and prevents the accidental removal of the plug 6 from the end of the expandable tube 1.

In its operation, gas for feeding the ion sources of the calutron flows through a vapor tube 4, entering through end portion 11 and exiting through end portion 12. When air pressure is applied from the source 10, the expandable core 1 presses outward, compressing the rubber tube 4 against the cavity walls, thus flattening the tube 4 and controlling the flow of gas through it. Therefore, the flow through tube 4 is inversely proportional to the pressure applied from the source 10.

Due to the manner in which the larger expandable core compresses a smaller flow tube over its entire surface area, a relatively large change in pressure exerted on the expandable core 1 is necessary to cause a small change in How through the flow tube 4. Under normal operating conditions, a pressure of 40 to 50 p.s.i. must be exerted on the core to regulate the flow of gas through the flow tube at a desirable volume. A relatively large change in pressure on the core is required to effect a small change in the flow through the vapor tube, and this feature enables the operator to control the flow at a constant rate down to less than 0.4 cc./ hour.

My improved leak valve can easily be repaired. The flow tube 4 and expandable core 1 can be replaced very quickly at nominal cost. These two parts appear to be the only points subject to wear. The prior art control valves require replacement of the entire valve, at great expense, when there is a failure.

My improved valve can be used with many gases. For example, the rubber flow tube 4 has been found to with stand a chlorine atmosphere very well with only a very slight hardening of the tube after 72 hours exposure. Another feature of this leak valve is that it can be adjusted remotely. By locating an air pressure regulating valve (not shown) near the control panel, the operator can regulate the pneumatic pressure applied through the inlet to my improved valve, located near the calutron 4 source to control the flow of gas to the ionization chamber while observing the controls. This permits a much more satisfactory means of adjustment than outlined above in connection with the prior art.

While the preferred embodiment of my invention has been described as used in a calutron, it is also useful in conventional mass spectrometers to control the gas input thereto. The scope of the invention is therefore to be drawn from the appended claims, and is not restricted to the single embodiment shown and described.

Having thus described my invention, I claim:

1. An adjustable leak valve comprising a housing provided with a cylindrical cavity therein, an expandable core disposed within said cavity, a resilient, flexible tube for connection to a source of gas, said tube being spirally wound on said core, the tube being in contact with the inner Wall of said cavity, and means connected to said core to expand saidw core, thereby compressing said tube against the said inner, wall of said cavity to change the cross sectional area of said tube.

2. An adjustable leak valve comprising a housing having a central bore therein, an expandable tubular core disposed within said bore, a resilient flexible tube for connection to a source of gas, said tube being wound around the outer surface of the core, said tube being adjacent to walls of the bore, a source for feeding gas to the tube, pneumatic means coupled to the core for applying pressure to expand it and press the tube against the walls of the cavity to restrict gas flow therethrough and regulate the passage of gas through the tube.

3. An adjustable leak valve comprising a divided housing having a cavity formed therein, an expandable tubular core disposed therein, said core having one end closed, a gas supply tube of resilient flexible material wound spirally about the outer surface of the core, a supply of gas coupled to the tube, and means for applying pneumatic pressure to the core for expanding it to press the tube against the walls of the cavity to constrict said tube and regulate the flow of gas therethrough.

References Cited by the Examiner UNITED STATES PATENTS 2,422,921 6/1947 Nier 13845 X 2,492,149 12/1949 Heuver 251-5 X 2,517,820 8/1950 Aagaard 251-5 X 2,827,919 3/1958 Rice 2Sl5 X 3,018,793 1/1962 Aagaard 2515 X FOREIGN PATENTS 649,146 1/1951 Great Britain.

ISADOR WEIL, Primary Examiner. 

1. AN ADJUSTABLE LEAK VALVE COMPRISING A HOUSING PROVIDED WITH A CYLINDRICAL CAVITY THEREIN, AN EXPANDABLE CORE DISPOSED WITHIN SAID CAVITY, A RESILIENT, FLEXIBLE TUBE FOR CONNECTION TO A SOURCE OF GAS, SAID TUBE BEING SPIRALLY WOUND ON SAID CORE, THE TUBE BEING IN CONTACT WITH THE INNER WALL OF SAID CAVITY, AND MEANS CONNECTED TO SAID CORE TO EXPAND SAID CORE, THEREBY COMPRESSING SAID TUBE AGAINST THE SAID INNER WALL OF SAID CAVITY TO CHANGE THE CROSS SECTIONAL AREA OF SAID TUBE. 